Wedge Threaded Steel Pipe Connection With Balanced Torque And Sealing
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Solution Overview
Problem
Existing threaded connections for steel pipes in deep oil wells face challenges in achieving high torque performance, tension performance, and sealability, with the wedge ratio's effect on these aspects not fully evaluated in prior art.
Innovation Solution
A threaded connection design with a wedge ratio between 3% and 7%, characterized by specific pitch and flank angle relationships between loading and stabbing flanks, ensures high torque performance, tension performance, and sealability by optimizing the thread geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a wedge thread with high torque performance is used, then torque performance is improved, but thread crest breakage may occur due to excessive stress concentration
Solution Approach 1:
The patent optimizes the wedge ratio parameter to a specific range (3-7%) to balance torque performance and thread crest strength. By controlling the difference between loading-flank pitch and stabbing-flank pitch within this range, the design achieves high torque transmission while preventing excessive stress concentration that would cause thread crest breakage
Solution Approach 2:
The patent applies different pitch values to different flanks of the thread (loading-flank vs stabbing-flank), creating local quality variations. The loading-flank has a larger pitch than the stabbing-flank, which allows the thread to generate high torque through the loading flank while the stabbing flank maintains tighter engagement to prevent crest breakage
2Power
If the wedge ratio is increased to improve torque performance, then torque performance is improved, but sealability may deteriorate due to altered contact pressure distribution
Solution Approach 1:
The patent carefully controls the wedge ratio parameter within the 3-7% range to maintain optimal seal contact pressure. This parameter optimization ensures that the metal seal elements maintain sufficient contact pressure for sealability while still achieving high torque performance through the wedge thread mechanism
3Power
If the pitch difference between loading and stabbing flanks is increased, then wedge ratio and torque performance are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a moderate wedge ratio range (3-7%) that balances the pitch difference between flanks. This controlled parameter range achieves sufficient torque performance while keeping manufacturing precision requirements practical and achievable with standard machining capabilities
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The optimized wedge ratio enhances torque performance, tension performance, and sealability, while preventing thread crest breakage, and maintains effective seal contact pressures, as demonstrated through finite element analysis and real-pipe tests.
Implementation Method 1
the amount of interference causes the diameter of the pin seal to decrease and the diameter of the box seal to increase. Each of the seals tries to recover their original diameters and thus produces elastic recovery forces, which produce contact pressures on the seals such that the seals tightly contact each other along the entire circumference, thereby providing sealability
Data Source
AI summary
A threaded connection for steel pipe that provides high torque performance, high tension performance and high sealability is provided. A threaded connection 1 includes: a tubular pin 10 including a pin shoulder 12, a male thread 11 and a pin seal 13; and a tubular box 20 including a box shoulder 22, a female thread 21 and a box seal 23. The male and female threads 11 and 21 are constituted by wedge threads. The pin seal 13 is provided between the pin shoulder 12 and the male thread 11. The box seal 23 corresponds to the pin seal 13 and is located on the inner peripheral surface of the box 20. When the connection is made up, the pin shoulder 12 is spaced apart from the box shoulder 22. The threaded connection 1 satisfies the following expression, (1):3%≤(LP−SP)/LP≤7% (1).In expression (1), LP is the pitch between loading flanks 111 of the male thread 11, and SP is the pitch between stabbing flanks 112 of the male thread 11.